Film formation method and film formation apparatus for thin film

ABSTRACT

A method for forming a thin film having durability at a low cost is provided. A film formation apparatus  1  is used in the film formation method. The apparatus  1  comprises a vacuum container  11 , in which a substrate  100  is placed at a lower part, a vacuum pump  15  for exhaust inside the container  11 , a storage container  23  for storing a coating agent  21  provided outside the container  11 , a nozzle having an ejection part  19  capable of ejecting the coating agent  21  at its one end and a pressurizing means (a gas supply source  29 , etc.) for pressurizing a liquid surface of a coating agent  21  stored in the storage container  23 . A solution, which includes two or more kinds of materials including a first material (S 1 ) and a second material (S 2 ) having a higher vapor pressure (P 2 ) than a vapor pressure (P 1 ) of the S 1  and has a concentration of the first material being 0.01 wt % or more, is used as the coating agent  21 . The coating agent  21  is ejected to a substrate in an atmosphere with a pressure of P 2  or higher (excepting pressures higher than P 2  by one digit or more) and with an ejection pressure of 0.05 to 0.3 MPa.

This application is a U.S. national phase filing under 35 U.S.C. §371 of PCT Application No. PCT/JP2015/063081, filed on May 1, 2015, which is hereby incorporated by reference in its entirety by reference.

TECHNICAL FIELD

The present invention relates to a film formation method and apparatus for forming a thin film in a vacuum. The thin film includes, for example, an organic film and inorganic film, etc.

BACKGROUND ART

Use of a wet coating method, such as a paint-on method and dipping method, has been known as a film formation method for forming an organic or inorganic film as an example of a thin film on a surface of a substrate. For example, the patent document 1 proposes a film formation method for forming 10 to 400 nm-depth scratches to give a strip-shaped fine pattern in a predetermined direction on a surface of a glass or plastic substrate in the air, then, applying a coating liquid (dilute solution) prepared to have a predetermined composition and drying so as to form an antifouling film (organic film) having a predetermined composition on the finely patterned surface. Also, the patent document 2 proposes a film formation method for forming an inorganic titanium oxide film (inorganic film) by mixing titanium oxide particles in water to obtain a suspension, adjusting it to have a specific pH, then, applying the suspension to a support body and drying.

RELATED ART DOCUMENTS Patent Document

Patent Document 1: Japanese Unexamined Patent Publication (Kokai) No. H09-309745 Patent Document 2: Japanese Unexamined Patent Publication (Kokai) No. H06-293519

SUMMARY OF THE DISCLOSED SUBJECT MATTER

A dilute liquid having a low solute concentration is used as a coating liquid or suspension in the wet coating method. Therefore, a density of the film to be obtained after drying by heat becomes low and, along therewith, a function of the film to be formed is liable to be lost, which is a problem. For example, in an antifouling film coated by the wet coating method, a film formed on the outermost surface comes off easily by wiping and the oil repellency is lost in some cases.

On the other hand, a film formation method for forming a thin film on a substrate by using a vacuum vapor deposition method (dry coating method) may be also considered. When using this method, however, a highly vacuum condition has to be created when forming a film and an expensive evacuation system is required. As a result, film formation at a low cost is hard to be realized.

According to an aspect of the present invention, a film formation method and apparatus capable of forming a thin film having durability at a low cost are provided.

In the present invention, “ejection” means blowing out a liquid in a liquid state. “Ejection” also includes “spraying”, which is blowing out by spraying a liquid. In this “ejection”, a physical state and chemical state of a material in the liquid do not change before and after the ejection. Therefore, “ejection” has a different principle from that in vapor deposition, wherein a physical state of a material changes from liquid or solid to a gas, or from that in CVD, wherein a chemical state of a material changes.

The present inventors found that a durable thin film was able to be formed when ejecting a solution composed of two or more kinds of materials including a first material (S1) and a second material (S2) having a high vapor pressure (P2) than a vapor pressure (P1) of the S1, wherein a concentration of the first material (hereinafter, also referred to as “an S1 concentration”) is adjusted, in an atmosphere with a specific pressure (Pc) (a pressure of P2 or higher (not higher than P2 by one digit or more)) and with a predetermined ejection pressure. Also, they found that the specific pressure Pc mentioned above for ejecting the solution often belongs to a medium or low vacuum range, therefore, a durable thin film can be formed at a low cost comparing with the vapor deposition method, which requires to create a high vacuum condition when forming a film, and accomplished the present invention.

According to the first aspect of the present invention (the first invention), a film formation method of a thin film having the configuration below is provided. In this film formation method, it is on the premise that a thin film is formed on a substrate in a vacuum. Also, it has a feature that a solution including two or more kinds of materials (for example, a first material (S1), a second material (S2) and a third material (S3), . . . , etc. It will be the same hereinafter.) is ejected to a substrate in an atmosphere with a pressure (Pc) set based on vapor pressures (for example, P1, P2, P3, . . . , etc. It will be the same hereinafter.) of the respective materials (for example, S1, S2, S3, . . . , etc. It will be the same hereinafter.) composing the solution.

According to the second aspect of the present invention (second invention), a film formation apparatus having the configuration below is provided. It is on the premise that the film formation apparatus is used for forming a thin film on a substrate in a vacuum. The apparatus comprises a vacuum container, in which a substrate as a film formation subject is placed, an exhaust means for exhausting inside the vacuum container, a storage container for storing a solution including two or more kinds of materials, and a nozzle for ejecting the solution to a substrate placed inside the vacuum container. It is configured that, when a pressure inside the vacuum container becomes a pressure (Pc) set based on vapor pressures of respective materials composing the solution, the solution is ejected to the substrate from the nozzle.

In addition to the above, the present invention (the first and second inventions) uses a solution to be ejected to a substrate, wherein the solution includes as materials thereof a first material (S1) and a second material (S2) having a higher vapor pressure (P2) than a vapor pressure (P1) of the S1 and an S1 concentration is adjusted to a predetermined value (0.01 wt %) or higher. It is characterized that the solution is ejected to a substrate with an ejection pressure in a predetermined range (0.05 to 0.3 MPa) when a pressure (Pc) in the atmosphere is P2 or higher (except for pressures higher than P2 by one digit or more).

In the second invention, a substrate as a film formation subject may be placed at a lower part inside the vacuum container (that is, a lower part in the longitudinal direction) or on the side part inside the vacuum container (that is, a side part in the horizontal direction). An end (ejection part) of the nozzle may be arranged so as to be able to eject the solution downward (either vertically or obliquely) (hereinafter, also simply referred to as “ejection direction of the solution is downward”) when a substrate is placed at a lower part inside the vacuum container, or may be arranged so as to be able to eject the solution crosswise (either horizontal or obliquely) (hereinafter, also simply referred to as “the ejection direction of the solution is crosswise”) when the substrate is placed at a side part inside the vacuum container. Namely, in the second invention, a position of providing the ejection part is not limited.

It is the same also in the first invention, and the ejection direction of the solution may be either downward or crosswise.

In the second invention, an inline type having a conveying mechanism for conveying a substrate is also applicable. In the first invention, when performing film formation by the inline type having a conveying mechanism, productivity improves, which is advantageous.

According to the first invention, a solution composed of two or more kinds of materials including S1 and S2 (note that a relationship between P1 of S1 and P2 of S2 is P1<P2), wherein an S1 concentration is adjusted, is ejected to a film formation subject (substrate) with an ejection pressure in a predetermined range when a pressure Pc in an atmosphere is P2 or higher (except for pressures higher than P2 by one digit or more). When ejecting the solution under the pressure Pc, volatilization of S2 is caused on the substrate but that of S1 is not caused. Therefore, a thin film to be formed on the substrate becomes high in density. Namely, according to the first invention, a durable thin film can be formed at a low cost.

According to the second invention, a solution composed of two or more kinds of materials including S1 and S2 (note that a relationship between P1 of S1 and P2 of S2 is P1<P2), wherein an S1 concentration is adjusted, is ejected from a nozzle to a film formation subject (substrate) with an ejection pressure in a predetermined range when a pressure Pc in an atmosphere is P2 or higher (except for pressures higher than P2 by one digit or more). When ejecting the solution with the pressure Pc in the vacuum container, volatilization of S2 is caused while that does not happen to S1. Therefore, a thin film to be formed on the substrate becomes high in density. Namely, according to the second invention, a durable thin film can be formed at a low cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view showing an example of a film formation apparatus capable of implementing the method of the present invention.

DESCRIPTION OF NUMERICAL NOTATIONS

-   -   1 . . . film formation apparatus, 11 . . . vacuum container, 13         . . . pipe, 15 . . . vacuum pump (exhaust means), 16 . . .         controller, 17 . . . nozzle, 18 . . . pressure detection means,         19 . . . ejection part, 21 . . . coating agent, 23 . . . storage         container, 25 . . . liquid feed tube, 26 . . . valve, 27 . . .         pipe, 29 . . . gas supply source, 31 . . . substrate holder, 33         . . . roller (conveying mechanism), 100 . . . substrate

EXEMPLARY MODE FOR CARRYING OUT THE DISCLOSED SUBJECT MATTER

Below, an embodiment of the invention above will be explained based on the drawing.

<Configuration Examples of Film Formation Apparatus>

First, an example (the case wherein an ejection direction of a solution is downward) of the film formation apparatus of the present invention (the apparatus of the present invention) will be explained.

As shown in FIG. 1, a film formation apparatus 1 as an example of the apparatus of the present invention comprises a vacuum container 11, in which a substrate 100 as a film formation subject is placed. The vacuum container 11 is configured as a cavity body having an approximate parallelepiped shape in this example, however, the shape is not limited to that in the present invention.

An exhaust port for exhaustion (illustration is omitted) is provided near a lower end on a sidewall of a vacuum container 11. The exhaust port is connected to an end of a pipe 13, and the other end of the pipe 13 is connected to a vacuum pump 15 (exhaust means). The vacuum pump 15 may be any as long as being able to create a vacuum state from an air pressure to a medium vacuum (0.1 Pa to 100 Pa) or so, such as a rotary pump (oil rotary vacuum pump) in this example. It is not necessary to use pumps requiring a high cost for introduction, such as a turbo molecular pump (TMP) and an oil diffusion pump, which can produce a high vacuum state (lower than 0.1 Pa). Therefore, an apparatus cost can be reduced in this example.

The vacuum pump 15 operates by an instruction from a controller 16 (control means) and a vacuum degree (pressure) inside the container 11 is heightened by depressurizing through a pipe 13. In the vacuum container 11, a pressure detection means 18 (a pressure gauge, etc.) is provided for detecting a pressure inside the container 11. Information on the pressure inside the container 11 detected by the pressure detection means 18 is output to the controller 16 sequentially. When the controller 16 determines that the pressure inside the container 11 reached a predetermined value, it sends an operation instruction to a gas supply source 29 (explained later).

The pressure inside the container 11 may be also controlled, for example, by introducing an argon or other gas to the container 11 via a flow rate regulator (illustration is omitted), such as a mass flow controller (MFC), under monitoring by the pressure control unit (illustration omitted), such as an auto pressure controller (APC). Also, it may be configured to provide a valve (illustration omitted) in the middle of the pipe 13 connecting the exhaust port of the container 11 to the pump 15 so as to control the pressure in the container 11 by adjusting an opening degree of the valve in a state that the pump 15 is in operation.

In this example, it may be also configured that an opening/closing door (illustration omitted) is provided as a separation means capable of opening and closing at the lower part on the sidewall of the vacuum container 11 so as to be connected to a load lock chamber (illustration omitted) through the opening/closing door.

In this example, at an upper part inside the vacuum container 11, one end of a nozzle 17 is inserted downwardly and the other end of the nozzle 17 is exposed to outside the container 11. The one end of the nozzle 17 inside the container 11 is connected to an ejection part 19. Note that the number of nozzles 17 to be inserted to the container 11 is not limited. A plurality of nozzles 17 may be used for one container 11 depending on a size of the container 11 in some cases. In this example, when assuming that the extending direction of the nozzle 17 is a center axis, the ejection part 19 is preferably configured to be able to spray a coating agent 21 in a full conical shape or a fan shape, for example, at an angle θ which is 30 degrees or more and 80 degrees or less with respect to the center axis. Solution-state particles having a size of, for example, several hundreds μm are ejected from the ejection part 19.

At the other end of the nozzle 17 exposed to outside the container 11 is connected to an end of a liquid feed tube 25 whose other end is inserted to a storage container 23 for storing the coating agent 21 in a closed way. Thereby, it is configured that, when the valve 26 is open, the coating agent 21 fed through the liquid feed tube 25 from the storage container 23 is ejected to the lower part inside the container 11 from the ejection part 19 connected to one end of the nozzle 17.

In this example, the storage container 23 is connected to an end of a pipe 27 for gas supply in order to pressurize a liquid surface inside the container 23, and the other end is connected to a gas supply source 29.

The gas supply source 29 operates in response to an instruction from the controller 16 and supplies a gas to the pipe 27, so that the liquid surface in the storage container 23 is pressurized. Thereby, the liquid surface in the storage container 23 is pressurized and the coating agent 21 is fed to the liquid feed tube 25 due to the pressure in this example. Note that the mode is not limited to feeding the coating agent 21 by pressurizing like this in the present invention.

A substrate holder 31 for holding the substrate 100 as a film formation subject is arranged at a lower part in the vacuum container 11. The substrate holder 31 is supported by a conveying mechanism composed of a plurality of rollers 33, 33, . . . , etc. in this example, and the substrate holder 31 is movable inside the container 11 by operating the conveying mechanism. Note that moving here includes rotating in addition to straight-line move (as in this example). In the case of rotating, the substrate holder 31 may be configured, for example, to be a turntable style. The substrate holder 31 has a concave-shaped substrate holding surface on its inner surface, where a back surface of a substrate 100 (either one or more) as a film formation subject contacts, so that the substrate 100 is held.

In the present invention, distance D between the ejection part 19 and the substrate 100 is not particularly limited as long as it is a distance that the coating agent 21 to be ejected in a liquid state from the ejection part 19 can reach as a liquid to the substrate 100. It is because the distance from the ejection part 19 that the coating agent 21 can reach the substrate 100 changes due to various elements, such as a direction of the ejection part 19, initial speed of the coating agent 21 when ejected from the ejection part 19 and a vapor pressure (P2) of a second material (S2, explained later) at a normal temperature included in the coating agent 21.

In this example, wherein the ejection direction of the coating agent 21 is downward, an arrangement of the ejection part 19 and the substrate holder 31 are adjusted so that the distance D becomes about 300 mm or less, consequently, sufficient strength can be given easily to a thin film to be obtained and the level of durability is improved easily.

In this example, wherein the ejection direction of the coating agent 21 is downward, by arranging the ejection part 19 so that the distance D to the substrate 100 becomes 150 mm or more, an effective ejection range for the coating agent 21 is secured sufficiently, which contributes to suppress a useless consumption of the coating agent 21, and that consequently may contribute to a furthermore reduction of a film formation cost.

Note that in this example, wherein the ejection direction of the coating agent 21 is downward, when the distance D is too far, volatilization of a dilute agent (solvent) in the coating agent 21 arises in the middle of ejection and leveling after reaching to the substrate hardly occurs, consequently, a film distribution becomes uneven and film performance declines in some cases. When the distance D is too short, the effective ejection range becomes small in accordance therewith, so that a useless consumption of the coating agent 21 increases and film unevenness may be caused.

The controller 16 has a function of controlling a pressure inside the container for adjusting a vacuum degree (that is, a pressure at starting film formation) inside the container 11 by operating the vacuum pump 15 and the pressure detection means 18. Together therewith, the controller 16 also has a function of controlling a pressure for pressurizing a liquid surface for adjusting a pressure imposed to the liquid surface inside the storage container 23 by a gas to be supplied from the gas supply source 29. Note that the controller 16 also has a control function of operating and stopping the conveying mechanism composed of a plurality of rollers 33, etc.

<Film Formation Example>

Next, an example of the film formation method of the present invention (the method of the present invention) using the film formation apparatus 1 will be explained.

(1) First, a coating agent 21 is prepared. In this example, an example, wherein the coating agent 21 is composed of a solution including two kinds of materials, a first material (S1) and a second material (S2), will be explained. To compare S1 and S2, a component of a material for film forming (a constituting material of a thin film) is S1 and a component (a liquid) for S1 to be dissolved therein is S2 in the explanation below.

Note that a liquid is also included in S1 in addition to powder or other solid.

When the coating agent 21 is composed of a mixture of a liquid (for example, liquid A) and a liquid (for example, liquid B), even if a concentration (an amount of presence or a rate) of liquid A is higher than that of liquid B in the coating agent 21 (specifically, even if the concentration of liquid A is high as exceeding 50 wt %), liquid A constitutes S1 as long as it is a component of a material for film forming (constituting material of a thin film). Namely, a concentration itself in the solution is not an element for determining which is S1 and which is S2.

An organic film and inorganic film are examples of a thin film. An organic-inorganic hybrid film, etc. formed by a material having both an organic component and inorganic component are also included. As those thin films, an antifouling film, water repellent film, moistureproof film, organic EL film and titanium oxide film, etc. may be mentioned and, as respective constituting materials (corresponding to S1 in this example), for example, hydrophobic reactive organic compounds (organic compounds having at least one hydrophobic group and at least one reactive group capable of bonding with a hydroxyl group in one molecular), water repellent materials, moistureproof materials, organic EL materials and titanium oxides, etc. may be mentioned.

For example, as a hydrophobic reactive organic compound as a material capable of forming an antifouling film, which is an example of an organic-inorganic hybrid film, an organic silicon compound, etc. including a polyfluoroether group or a polyfluoroalkyl group may be mentioned. To raise product examples, OF-SR (oil repellent agent) and OF-110 (water repellent agent), etc. of Canon Optron Inc. may be mentioned.

Among the hydrophobic reactive organic compounds mentioned above, it is particularly preferable to select a substance (being liquid at a normal temperature) having a low vapor pressure (P1) at a normal temperature, such as 10⁻⁴ Pa or so or lower (preferably 0.8×10⁻⁵ Pa to 3×10⁻⁴ Pa or so and more preferably 10⁻⁴ Pa or lower).

S2 to be used is not particularly limited as long as a component S1 as a constituting material of various thin films mentioned above can be dissolved therein. When using a hydrophobic reactive organic compound including fluorine as S1, it is preferable to use as S2 a solvent, which also includes fluorine (a fluorine-type solvent), because the affinity becomes high.

As a fluorine-type solvent, for example, fluorine-modified aliphatic hydrocarbon-type solvent (perfluoroheptane, perfluorooctane, etc.), fluorine-modified aromatic group hydrocarbon-type solvent (m-xylenehexafloride, benzotrifluoride, etc.), fluorine-modified ether-type solvent (methylperfluorobutylether, perfluoro(2-butyltetrahydroflane), etc.), fluorine-modified alkylamine-type solvent (perfluorotributylamine, perfluorotripencylamine, etc.), etc. may be mentioned.

Among the fluorine-type solvents mentioned above, it is particularly preferable to select a substance having a very high vapor pressure (P2) at a normal temperature, for example, 10³ Pa or so or higher (preferably 0.8×10³ Pa or higher and an atmosphere pressure of lower than 1.01325×10⁵ Pa or so, more preferably 6.0×10³ Pa to 1.6×10⁴ Pa or so) and excellent volatility at a normal temperature.

Fluorine-type solvent may be used alone or in combination of two or more kinds. When mixing two or more kinds to use, it is preferable that they are selected so that the mixture as a whole has a vapor pressure in the range explained above.

In the present invention, a coating agent 21 to be used is required to have a concentration of S1 (S1 concentration) being 0.01 wt % or more. When the S1 concentration is too low, even if a liquid ejection pressure is adjusted properly, in the present invention, wherein a film formation start pressure (explained later. It will be the same below.) is P2 or higher (except for pressures higher than P2 by one digit or more), the coating agent 21 drops undesirably from the ejection part 19 before starting film formation and film formation cannot be performed properly in some cases. Furthermore, even if film formation is attained, a decline of a film density of the thin film is hard to be prevented.

In the present invention, an S1 concentration in the coating agent 21 may be 0.01 wt % or more, preferably 0.03 wt % or more and furthermore preferably 0.05 wt % or more. When using a coating agent 21 with an S1 concentration of 0.03 wt % or more, a durability level of a thin film to be obtained is improved easily even if a film formation start pressure is P2 or higher (except for pressures higher than P2 by one digit or more).

The upper limit of the S1 concentration may be determined to be in a range of not causing so-called liquid clogging by sticking inside the liquid feed tube 25 or ejection part 19 in consideration of kinds of S1 and S2 to be used, an inner diameter and length of the liquid feed tube 25 and the configuration of the ejection part 19, etc. When using, for example, a hydrophobic reactive organic compound as S1 and a fluorine-type solvent as S2, unless the S1 concentration is 100 wt % (namely, only S1 and zero S2), even if the upper limit is set close to 100 wt %, film formation is possible without causing any liquid clogging inside the liquid feed tube 25 and ejection part 19 by devising a film formation start pressure, liquid ejection pressure, an inner diameter and length of the liquid feed tube 25 and the configuration of the ejection part 19, etc. and a sufficient film performance can be also obtained. Therefore, in this example, an upper limit of the S1 concentration may be less than 100 wt %, preferably 70 wt %, more preferably 40 wt % and furthermore preferably 10 wt %.

Particularly preferably, for example, it is 2 wt % or less, preferably 1 wt % or less and more preferably 0.1 wt % or less. When the S1 concentration is 2 wt % or less, film unevenness is hardly caused on the film formation surface (adherence of excessive material, which does not form a film) of the film formation subject (a plurality of substrates 100), consequently, a useless consumption of the coating agent 21 can be suppressed and a cost of forming a thin film can be reduced furthermore easily.

Note that when the S1 concentration is too high, depending on the film formation start pressure and liquid ejection pressure, an S1 component sticks inside the liquid feed tube 25 and ejection part 19 to cause so-called liquid clogging in some cases.

Viscosity of the coating agent 21 to be used is not particularly limited and may be adjusted properly in consideration of an inner diameter and length of the liquid feed tube 25 and the configuration of the ejection part 19, etc., so that the coating agent 21 flows smoothly in the liquid feed tube 25 and is ejected properly from the ejection part 19, therefore, the coating agent 21 does not stick inside the liquid feed tube 25 or ejection part 19 and so-called liquid clogging is not caused.

(2) Next, the prepared coating agent 21 is placed in the storage container 23. Also, a plurality of substrates 100 are held on the concave portion of the substrate holder 31 outside the container 11 in this example.

As the substrates 100, which can be held and fixed on the substrate holder 31, a glass substrate, metal substrate and plastic substrate, etc. may be mentioned. A non-heating type film formation (the method of not heating inside the container 11 at film formation) may be selected depending on a kind of the substrates 100. When selecting a non-heating type film formation, plastic substrates are also applicable in addition to glass substrates and metal substrates. As the substrates 100, those processed to have, for example, a plate shape or lens shape, etc. may be used. On the substrates 100, wet cleaning may be performed before fixing them to the substrate holder 31 or after fixing but before starting film formation.

(3) Next, the substrate holder 31 holding the plurality of substrates 100 is set inside the container 11 (in the case of batch processing). During this, by opening the opening/closing door (explained above) provided at a lower part on the sidewall of the container 11 and operating the conveying mechanism (roller 33), the substrate holder 31 holding the substrates 100 may be transferred from a load lock chamber and set in the container 11. After that, the pump 15 is operated by an instruction from the controller 16 to start exhausting inside the vacuum container 11.

Note that the substrate holder 31 does not necessarily stay still in the container 11 but moves at a predetermined conveying speed inside the container 11 even during film formation (inline type) in the case of continuous processing. The faster the conveying speed is, the more advantageous in terms of productivity. However, it is preferable to be, for example, 50 to 90 mm/second or so in terms of an effective use of the film formation agent (film formation material of a thin film and corresponding to S1 in this example) and film performance, etc.

The controller 16 detects a pressure (Pc) inside the container 11 sequentially by an output from the pressure detection means 18. In this example, when it is determined that the pressure Pc in the container 11 becomes higher than a vapor pressure (P2) of S2 included in the coating agent 21 or higher (P2<Pc), it is preferable to maintain this state by control by the function of controlling a pressure inside the container and the operation start instruction is sent to the gas supply source 29. The gas supply source 29, which received the operation instruction, supplies a gas into the pipe 27 and the gas pressurizes a liquid surface inside the storage container 23. As a result, the coating agent 21 is fed through the liquid feed tube 25 by the pressure, introduced to the nozzle 17, then ejected from the ejection part 19 to inside the container 11.

In the present invention, the pressure Pc in the container 11 above, in which the coating agent 21 is ejected, may be set to be less than a pressure higher than P2 by one digit or more. Thereby, arising of a film defect can be prevented effectively.

In the case of performing film formation under a too high pressure (for example, a pressure higher than P2 by one digit or more) comparing with a vapor pressure P2 of the solvent S2 at a normal temperature, a solvent remained during film formation is removed by a drying step, etc. after film formation, however, a film is not formed on that part (a solute component does not adhere uniformly, which results in a film defect). When the solute component does not adhere uniformly on the substrates 100, a part with no thin film formed thereon exists on the substrates 100, film peeling arises from this point with no film exists during friction, and improvement of film durability cannot be expected.

In the present invention, it is preferable to impose a pressure (ejection pressure) to the coating agent 21 when ejecting from the ejection part 19. By imposing an ejection pressure, in the present invention, wherein a film formation start pressure is P2 or higher (except for pressures higher than P2 by one digit or more), ejection can be made with a liquid ejection form (ejection shape) being most effectively spread (shower-like shape), a useless consumption of the liquid is reduced, thin film formation at a low cost can be realized, and the productivity is improved easily without imposing any ejection pressure to the coating agent 21. Note that it is preferable to use a spray nozzle and furthermore to eject the coating agent 21 with an ejection pressure (gauge pressure) of 0.05 to 0.3 MPa in terms of stabilizing a shape of the ejection. By ejecting with a specific ejection pressure, the ejection shape is furthermore stabilized, a useless consumption of the liquid is furthermore reduced, thin film formation at a furthermore lower cost can be realized and the production efficiency is improved furthermore easily. To eject the coating agent 21 with the specific ejection pressure, a gas is fed to the pipe 27 so that the pressurization on the liquid surface in the storage container 23 becomes 0.05 to 0.3 MPa.

Ejection duration of the coating agent 21 from the ejection part 19 is not limited as it changes depending on a size and the number of the substrates 100. A thickness of a thin film to be formed on the substrates 100 is not limited, either. It is because it changes depending on a kind of materials to be included in the coating agent 21 and the ejection duration of the coating agent 21, etc.

In this example, when ejecting the coating agent 21 to the substrates 100 from the ejection part 19 positioned away from the substrates 100 by distance D, the reason why it is preferable to adjust an S1 concentration of the coating agent 21 and an ejection pressure to be in predetermined ranges (the S1 concentration to be 0.01 wt % or more and the ejection pressure to be 0.05 to 0.3 MP) when controlling the pressure Pc inside the container 11 to be in a predetermined range (P2 or higher (except for pressures higher than P2 by one digit or more)) at starting ejection (that is, film formation) is because if the S1 concentration in the coating agent 21 and the ejection pressure are not adjusted in the case, where a pressure Pc in the container 11 at start ejecting is P2 or higher, a decline of a film density of a thin film to be obtained on a substrate 100 cannot be prevented and preferable film formation cannot be performed.

The mechanism that a film density of a thin film is declined is as explained below. When setting Pressure Pc in the container 11 to be P2 at starting ejection, S2 in the coating agent 21 sometimes remains on the substrate 100 if an S1 concentration in the coating agent 21 and an ejection pressure are not adjusted. It is considered that the S2 remained on the substrate 100 is volatilized during next drying step, which induces a film-lacking state, consequently, the film density of the thin film declines.

In this example, since the coating agent 21, wherein an S1 concentration is adjusted to be in a predetermined range, is used and ejected with a predetermined ejection pressure, even if the pressure Pc in the container 11 is controlled to be P2 or higher at starting ejection, S2 in the coating agent 21 does not remain on the substrate 100 and the film-lacking state can be prevented, so that a decline of the film density of the thin film can be prevented.

As a thin film to be formed in this example, as explained above, an antifouling film, water repellent film, moistureproof film, organic EL film and titanium oxide film, etc. may be mentioned as examples. The present invention is a film formation method able to be applied to all compounds including organic materials, inorganic materials, organic-inorganic hybrid materials, etc. Below, the case where a thin film to be formed in this example is an antifouling film (an example of an organic-inorganic hybrid film) will be explained.

An antifouling film is a film provided with water repellency and oil repellency and has a function of preventing adhesion of oil stain. Here, “preventing adhesion of oil stain” means not only that oil stain does not adhere but it can be wiped off easily when stain adheres. Namely, an antifouling film keeps oil repellency. Specifically explaining, a durability level of an antifouling film has been improved most, such that even after reciprocating steel wool #0000 for more than 2000 times (preferably 4000 times and more preferably 6000 times) with a load of 1 kg/cm² on an antifouling film, an ink by an oily-ink pen can be wiped off.

The reason why durability is improved as explained above is because, when using a coating agent 21 adjusted to have an S1 concentration and ejection pressure in predetermined ranges and ejecting it to the substrates 100 from the ejection part 19 at a position away by distance D, the pressure Pc in the container 11 at starting ejection is adjusted to be in a predetermined range (P2 or higher (except for pressures higher than P2 by one digit or more)), so that surfaces of the substrates 100 are fully covered with constituent molecules (thin film molecules) of an S1 component to eliminate a part with no thin film existing on the thin film.

As explained above, according to the film formation method using the film formation apparatus 1 of the present example in the case where the ejection direction of the coating agent 21 is downward, a coating agent 21 obtained by mixing S1 and S2 and adjusting an S1 concentration therein is used and ejected to the substrates 100 under a specific pressure Pc, which is a vapor pressure P2 of S2 or higher (excepting pressures higher than P2 by one digit or more) and with an ejection pressure in a predetermined range (0.05 to 0.3 MPa) so as to form a thin film. According to the film formation method in this example, the coating agent 21 ejected from the ejection part 19 reaches the substrates 100 while keeping the solution state, a solvent component evaporates after reaching the substrates 100 to form a film (thin film) and densified. As a result, it is possible to form a thin film having an improved durability level on each substrate 100 at a low cost.

When the thin film to be formed by the method of this example is an antifouling film, according to the antifouling film, constituents of the antifouling film can remain effectively even if fingerprints or other oil adhered to its surface are wiped off with a heavy load (a load of, for example, 1 kg/cm² or so).

A thin film to be formed in the method of the present example is not limited to an antifouling film and there is an example of forming an inorganic film, as well. In the case of a suspension liquid of 4 g/litter prepared by mixing titanium oxide particles in water (S1 is titanium oxide particles and S2 is water. A vapor pressure of water is 3000 Pa or so at a normal temperature), when the pressure Pc in the container 11 is set to 3000 Pa and ejecting the suspension liquid with an ejection pressure of 0.2 MPa to perform film formation, a titanium oxide film having a preferable optical characteristic is formed, wherein a refractive index is 2.400 with a light having a wavelength of 550 nm. It is considered that, by using a suspension liquid, wherein a titanium oxide particle concentration was adjusted to be in a predetermined range, and ejecting the same with an ejection pressure of 0.2 MPa when a pressure Pc inside the container was 3000 Pa, a fine inorganic titanium oxide film was formed and a preferable optical characteristic was obtained.

Other Embodiment

The film formation apparatus of the present invention is not limited to the mode of the film formation apparatus 1 explained above (the ejection direction of the coating agent 21 is downward) and the nozzle 17 may be arranged in the crosswise direction (the ejection direction of the coating agent 21 is crosswise). In the crosswise case, for example, one end of the nozzle 17 may be inserted in the horizontal direction from a side into the vacuum container 11 and the other end of the nozzle 17 may be exposed to the outside of the sidewall of the container 11. Alternatively, after attaching a rotatable member (illustration omitted) to around the middle of the nozzle 17 in the longitudinal direction so that a part below (including the ejection part 19) becomes rotatable, for example, by ±90 degrees or so, it may be arranged that one end (to which the ejection part 19 is connected) of the nozzle 17 is inserted downwardly from above into the vacuum container 11 and the other end of the nozzle 17 is exposed to the outside of the container 11. In either way, when the direction of installing the nozzle 17 is crosswise, the substrate holder 31 is arranged in the vacuum container 11 so that the surface of holding substrates 100 faces to the ejection part 19 connected to the end of the nozzle 17.

Alternatively, the substrate holder 31 may be configured to be movable and, separately from that, the nozzle 17 may be configured movable by a not shown conveying mechanism. In that case, this film formation means can be applied also to the mode wherein the nozzle 17 side moves.

EXAMPLES

Next, specific examples of the embodiments of the invention explained above will be given to explain the present invention in further detail.

Experimental Examples 1 to 6 1. Production of Antifouling Film Samples

The film formation apparatus 1 shown in FIG. 1 was used and two substrates 100 (glass substrates having a size of 50 mm×100 mm) were set on the substrate holding surface of the substrate holder 31.

Coating agents ‘a’ to ‘e’ having compositions described in Table 1 were prepared.

TABLE 1 S1 S2 25° C. 25° C. Vapor Vapor S1 Coating Pressure Pressure Concentration Agent Kind P1 (Pa) Kind P2 (Pa) (wt %) a Oil 10⁻⁵ Solvent 1 1.6 × 10⁴ 0.05 Repellent Agent 1 b Oil 10⁻⁵ Solvent 2 6.0 × 10³ 0.05 Repellent Agent 2 c Oil 10⁻⁵ Solvent 2 6.0 × 10³ 0.05 Repellent Agent 1 d Oil 10⁻⁵ Solvent 1 1.6 × 10⁴ 0.05 Repellent Agent 2 e Oil 10⁻⁵ Solvent 2 6.0 × 10³ 55 Repellent Agent 2

Note that, in Table 1, “oil repellent agent 1” is a surface antifouling coating agent (manufactured by DAIKIN INDUSTRIES, ltd., Product Name: Optool DSX, component: fluorine-containing organosilicon compound), “oil repellent agent 2” is a fluorine-type antifouling coating agent (manufactured by Shin-Etsu Chemical Co., Ltd., Product Name: KY-178, component: fluorine-containing organosilicon compound), “Solvent 1” is a fluorine-type solvent (manufactured by Sumitomo 3M Limited, Product Name: Novec7200) and “Solvent 2” is a fluorine-type solvent (manufactured by Sumitomo 3M Limited, Product Name: Novec7300).

Pressure Pc in the container 11 at starting film formation, distance D and other film formation condition are shown in Table 2. As the ejection part of the nozzle, a spray nozzle capable of ejecting solution-state particles in a size of 140 to 260 nm was used, and ejection duration of a coating agent was all 30 seconds. Then, samples of respective experimental examples, which are antifouling films having a thickness of 10 to 15 nm formed on substrates 100, were obtained.

Note that, in the experimental examples 1 to 3, an antifouling film was formed in a state that the substrate holder 31 having substrates 100 set thereon was still in the vacuum container 11 (batch processing). In the experimental examples 4 to 6, the holder 31 having the substrates 100 set thereon was conveyed in the vacuum container 11 while performing film formation (continuous processing).

2. Evaluation 2-1. Durability of Antifouling Film

On a surface of an antifouling film of each of the obtained experimental example samples, 1 cm² of steel wool (SW) #0000 was placed and reciprocated (friction) with a load of 1 kg/cm² on a 50 mm straight line at a rate of reciprocating one time per one second. After repeating the reciprocating operation for 3500 times, a contact angle of pure water on the antifouling surface was measured. Also, a contact angle of pure water on the antifouling surface was measured immediately after film formation. The value of the contact angle was a contact angle after 1 minute from dropping of pure water and was an average value of measurement values obtained by repeating dropping and measuring for 5 times. The results are shown in Table 2.

2-2. Maximum Times of Frictional Reciprocating of Antifouling Film

On a surface of an antifouling film of each of the obtained experimental example samples, 1 cm² of steel wool (SW) #0000 was placed and reciprocated (friction) with a load of 1 kg/cm² on a 50 mm straight line at a rate of reciprocating one time per one second. Every 100 times of the reciprocating operation, a line was drawn with an oily-ink pen (organic solvent-type marker, Product Name: Mackee Ultrafine, manufactured by ZEBRA CO., LTD.) on the test surface (antifouling film surface) and whether or not the organic solvent-type ink of the oily-ink marker was able to be wiped off was evaluated. As the results, the maximum times of frictional reciprocating when the organic solvent-type ink was able to be wiped off are shown in Table 2.

TABLE 2 Evaluation on Antifouling Film Film Formation Condition Contact Angle Film (degree) Coating Agent Substrate Formation Pressurization Immediately Maximum S1 Convey Start (Ejection After After Times of Experimental Concentration Rate Distance Pressure Pc Pressure) Film SW Frictional Example Kind (wt %) (mm/s) D (mm) (Pa) (MPa) Formation Friction Reciprocating 1 a 0.05 0 220 20000 0.1 115.2 113.6 3500 or more 2 b 0.05 0 220 7000 0.1 116.2 113 3500 or more 3 b 0.05 0 220 101325 0.1 111.3 40.6 500 (Atmospheric Pressure) 3a b 0.05 0 300 70000 0.1 110.2 54.4 500 3b b 0.05 0 220 7000 0.03 80.2 — 500 4 b 0.05 40 300 7000 0.1 116.2 109.7 3500 or more 4a e 55 40 300 600 0.1 113.8 102.2 3500 or more 5 b 0.05 80 300 7000 0.1 110 98.8 3500 or more 6 b 0.05 100 300 7000 0.1 105.1 45.6 2000 

3. Consideration 3-1. Batch Processing Cases (Experimental Examples 1 to 3b)

As shown in Table 1 and Table 2, in the experimental examples 1 and 2 (ejection in a low vacuum), wherein the S1 concentration of the coating agent and the pressure Pc at ejecting the coating agent were adjusted properly, almost no decline was observed on the contact angle on the antifouling surface after the SW friction from that immediately after the film formation, and the durability was extremely excellent. Also, the maximum times of frictional reciprocating was sufficient as 3500 times or more, and it was confirmed that a wear resistant property sufficient for practical use was provided.

On the other hand, in the experimental example 3 wherein Pc was too higher than P2 (sprayed at an atmospheric pressure) and in the experimental example 3a with a pressure higher than P2 by one digit or more, a contact angle on the antifouling surface declined largely after SW friction from that immediately after film formation. Also, the maximum times of frictional reciprocating was extremely small and it was confirmed that durability was not given.

Also, although the Pc was in a proper range, when the ejection pressure of the coating agent is too low (experimental example 3b), a sufficient contact angle was not obtained on the antifouling film surface already immediately after film formation. Also, the number of reciprocating times was extremely small and it was confirmed that durability was not obtained.

3-2. Continuous Processing Cases (Experimental Examples 4 to 6)

It was confirmed that, when conveying speed of the substrates becomes high, durability of the antifouling film declines and the maximum times of frictional reciprocating is liable to be less. The experimental example 5 exhibited good balance between a film performance and productivity. 

1. A film formation method for forming a thin film on a substrate in a vacuum, wherein a solution, which is composed of two or more kinds of materials including a first material (S1) and a second material (S2) having a higher vapor pressure (P2) than a vapor pressure (P1) of the S1 and has a concentration of the first material being 0.01 wt % or more, is ejected to a substrate in an atmosphere with a pressure of P2 or higher (excepting pressures higher than P2 by one digit or more) and with an ejection pressure of 0.05 to 0.3 MPa.
 2. The film formation method according to claim 1, wherein film formation is performed by an inline type having a conveying mechanism.
 3. A film formation apparatus used for forming a thin film on a substrate in a vacuum, comprising a vacuum container wherein a substrate as a film formation subject is placed, an exhaust means for exhausting inside the vacuum container, a storage container for storing a solution, which is composed of two or more kinds of materials including a first material (S1) and a second material (S2) having a higher vapor pressure (P2) than a vapor pressure (P1) of the S1 and has a concentration of the first material being 0.01 wt % or more, a nozzle for ejecting the solution to the substrate; and a pressurizing means for pressurizing a surface of a liquid stored in the storage container; wherein it is configured that the solution is ejected from the nozzle by pressurizing the surface of the liquid inside the storage container with 0.05 to 0.3 MPa when a pressure inside the vacuum container becomes a pressure of P2 or higher (excepting pressures higher than P2 by one digit or more).
 4. The film formation apparatus according to claim 3, being an inline type provided with a conveying mechanism for conveying a substrate. 